bims-plasge Biomed News
on Plastid genes
Issue of 2018‒08‒19
five papers selected by
Vera S. Bogdanova
Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences

  1. Plant Cell Rep. 2018 Aug 11.
      KEY MESSAGE: Rice rss1 complementation assays show that wheat TdRL1 and RSS1 are true functional homologs. TdRL1 over-expression in Arabidopsis conferred salt stress tolerance and alleviated ROS accumulation. Plants have developed highly flexible adaptive responses to their ever-changing environment, which are often mediated by intrinsically disordered proteins (IDP). RICE SALT SENSITIVE 1 and Triticum durum RSS1-Like 1 protein (TdRL1) are both IDPs involved in abiotic stress responses, and possess conserved D and DEN-Boxes known to be required for post-translational degradation by the APC/Ccdc20 cyclosome. To further understand their function, we performed a computational analysis to compare RSS1 and TdRL1 co-expression networks revealing common gene ontologies, among which those related to cell cycle progression and regulation of microtubule (MT) networks were over-represented. When over-expressed in Arabidopsis, TdRL1::GFP was present in dividing cells and more visible in cortical and endodermal cells of the Root Apical Meristem (RAM). Incubation with the proteasome inhibitor MG132 stabilized TdRL1::GFP expression in RAM cells showing a post-translational regulation. Moreover, immuno-cytochemical analyses of transgenic roots showed that TdRL1 was present in the cytoplasm and within the microtubular spindle of mitotic cells, while, in interphasic cells, it was rather restricted to the cytoplasm with a spotty pattern at the nuclear periphery. Interestingly in cells subjected to stress, TdRL1 was partly relocated into the nucleus. Moreover, TdRL1 transgenic lines showed increased germination rates under salt stress conditions as compared to wild type. This enhanced salt stress tolerance was associated to an alleviation of oxidative damage. Finally, when expressed in the rice rss1 mutant, TdRL1 suppressed its dwarf phenotype upon salt stress, confirming that both proteins are true functional homologs required for salt stress tolerance in cereals.
    Keywords:  Abiotic stress; Cellular localization; Durum wheat TdRL1; Oxidative stress; RSS1; Salt
  2. Plant Cell Rep. 2018 Aug 11.
      KEY MESSAGE: The dynamic alterations of the physiological and molecular processes in reproductive stage soybean indicated the dramatic impact caused by drought. Drought is a major abiotic stress that limits soybean (Glycine max) production. Most prior studies were focused on either model species or crops that are at their vegetative stages. It is known that the reproductive stage of soybean is more susceptible to drought. Therefore, an understanding on the responsive mechanisms during this stage will not only be important for basic plant physiology, but the knowledge can also be used for crop improvement via either genetic engineering or molecular breeding. In this study, physiological measurements and RNA-Seq analysis were used to dissect the metabolic alterations and molecular responses in the leaves of soybean grown at drought condition. Photosynthesis rate, stomata conductance, transpiration, and water potential were reduced. The activities of SOD and CAT were increased, while the activity of POD stayed unchanged. A total of 2771 annotated genes with at least twofold changes were found to be differentially expressed in the drought-stressed plants in which 1798 genes were upregulated and 973 were downregulated. Via KEGG analysis, these genes were assigned to multiple molecular pathways, including ABA biogenesis, compatible compound accumulation, secondary metabolite synthesis, fatty acid desaturation, plant transcription factors, etc. The large number of differentially expressed genes and the diverse pathways indicated that soybean employs complicated mechanisms to cope with drought. Some of the identified genes and pathways can be used as targets for genetic engineering or molecular breeding to improve drought resistance in soybean.
    Keywords:  Drought; Reproductive stage; Soybean; Transcriptome
  3. Plant Cell. 2018 Aug 10. pii: tpc.00312.2018. [Epub ahead of print]
      The plastid-localized phosphoglucose isomerase isoform PGI1 is an important determinant of growth in Arabidopsis, probably due to its involvement in synthesis of plastidial isoprenoid derived hormones. We have tested the possibility that it also influences seed yields, and several associated hypotheses. Gene expression analyses showed that PGI1 is strongly expressed in maturing seed embryos and vascular tissues. PGI1-null pgi1-2 plants had ca. 60% lower seed yields than wild type (WT) plants. They produced fewer inflorescences, and thus fewer siliques and seeds per plant. These traits were associated with low contents of bioactive gibberellins (GAs). Accordingly, WT phenotypes could be restored by exogenous GA application. pgi1-2 seeds were lighter and accumulated ca. 50% less fatty acids (FAs) and ca. 35% less proteins than WT seeds. Seeds of CK-deficient 35S:AtCKX1 and GA-deficient ga20ox1 ga20ox2 mutants did not accumulate low levels of FAs, and exogenous application of BAP and GAs did not rescue the reduced weight and FA content of pgi1-2 seeds. Seeds from reciprocal crosses between pgi1-2 and WT plants accumulated WT levels of FAs and proteins. Our results show that PGI1 is an important determinant of Arabidopsis seed yield due to its involvement in two processes: GA-mediated reproductive development and the metabolic conversion of plastidial glucose-6-phosphate to storage reserves in the embryo.
  4. Plant Cell Rep. 2018 Aug 11.
      KEY MESSAGE: OsHSP50.2, an HSP90 family gene up-regulated by heat and osmotic stress treatments, positively regulates drought stress tolerance probably by modulating ROS homeostasis and osmotic adjustment in rice. Heat-shock proteins (HSPs) serve as molecular chaperones for a variety of client proteins in abiotic stress response and play pivotal roles in protecting plants against stress, but the molecular mechanism remains largely unknown. Here, we report an HSP90 family gene, OsHSP50.2, which acts as a positive regulator in drought stress tolerance in rice (Oryza sativa). OsHSP50.2 was ubiquitously expressed and its transcript level was up-regulated by heat and osmotic stress treatments. Overexpression of OsHSP50.2 in rice reduced water loss and enhanced the transgenic plant tolerance to drought and osmotic stresses. The OsHSP50.2-overexpressing plants exhibited significantly lower levels of electrolyte leakage and malondialdehyde (MDA) and less decrease of chlorophyll than wild-type plants under drought stress. Moreover, the OsHSP50.2-overexpressing plants had significantly higher SOD activity under drought stress compared with the wild type. These results imply that OsHSP50.2 positively regulates drought stress tolerance in rice, probably through the modulation of reactive oxygen species (ROS) homeostasis. Additionally, the OsHSP50.2-overexpressing plants accumulated significantly higher content of proline than the wild type under drought stress, which contributes to the improved protection ability from drought stress damage via osmotic adjustment. Our findings reveal that OsHSP50.2 plays a crucial role in drought stress response, and it may possess high potential usefulness in drought tolerance improvement of rice.
    Keywords:  Drought tolerance; Heat-shock protein; Oryza sativa; OsHSP50.2; Reactive oxygen species
  5. Int J Biol Macromol. 2018 Aug 08. pii: S0141-8130(18)32919-2. [Epub ahead of print]
      Metallothioneins (MTs) are involved in cellular homeostasis of essential metal ions and detoxification of nonessential metal ions. We report here the identification of four MT genes, CtMT1, CtMT2, CtMT3 and CtMT4, encoding CtMT1, CtMT2, CtMT3 and CtMT4 proteins, respectively, from the industrial guar crop. The primary structures of last three proteins were similar to those of respective MT proteins of other plants but the CtMT1 protein primary structure was different from the other plant MT1 proteins in having an additional C-X-C motif. The four MT genes showed tissue specific expression patterns suggesting their specific roles in different tissues. High expression of CtMT1 gene was observed in roots and nodules whereas CtMT2 and CtMT3 genes showed high expression in leaves. The expression of CtMT4 gene was high in seeds. The qRT-PCR studies revealed upregulation in expression of CtMT1 gene under drought stress. Recombinant CtMT1 protein was produced in E. coli Rosetta cells and purified by metal affinity chromatography. The purified protein showed antioxidant property and the order of its metal ion binding affinities was Cu2+ > Zn2+ > Fe2+ > Cd2+. This information about CtMT1 protein is expected to be useful in understanding its role in drought tolerance and other physiological processes of guar.
    Keywords:  Drought tolerance; Hydroxyl radicals; Metal ion binding; Metallothionein; Motif; Reactive oxygen species